The present invention relates generally to the field of tools and, more particularly, to wrenches. Still more particularly, the present invention includes an adjustable wrench for grasping a nut, a bolt head, or the like, and for applying a turning force thereto.
Throughout the years, the widespread use of nuts, bolts or the like has resulted in the development of a great number of wrenches varying in size, shape or operating mechanism. One type of wrench has grasping mouths of fixed size, whereby a particular wrench can be used for performing an operation on a particular size object only. An advantage of such wrenches is that both jaws are integrally connected to the body of the wrench and therefore, they are not subject to play or movement caused by the pressure exerted on them during operation. However, the same wrenches have the disadvantage that one wrench may be used for a particular size object only and therefore, one must have many different wrenches for the different size objects. In order to overcome this difficulty, adjustable wrenches have been developed so that by adjusting the opening of the grasping mouth of the wrench, one may use the same tool to apply a turning force on objects of various sizes. Such adjustable wrenches are disclosed in U.S. Pat. Nos. 109,913, 341,503, 648,769, 670,890, 1,185,911, 1,468,913, 2,774,271 and 3,563,118.
In general, adjustable wrenches include a fixed jaw and a movable jaw that may be adjusted to different positions to form a mouth opening therebetween suitable for a particular operation on a particular size nut, bolt head or the like. During the turning operation, the force exerted by the jaws on the nut and consequently, the reaction force therefrom is of great magnitude biasing the movable jaw away from the fixed jaw. Therefore, unless provisions are made to prevent it, the movable jaw tends to move in a direction away from the fixed jaw, thereby causing the disengagement of the object being turned.
In the prior art, attempts were made to develop a mechanism for preventing the movement of the movable jaw away from the fixed jaw during turning. U.S. Pat. No. 109,913 discloses a wrench which includes a fixed jaw, a guide member, a movable jaw sliding on the guide member and a lever pivotally attached to the movable jaw having a pin extending therefrom. The movable jaw is kept in a desired position by pressing the lever towards the guiding member to engage the pin with the guiding member and to prevent sliding of the movable jaw on the guide member. One difficulty with this wrench is that this sliding prevention mechanism cannot withstand the biasing forces exerted on the movable jaw during operation resulting in the displacement of the movable jaw and the disengagement of the object. Furthermore, this wrench requires a continuous usage of the operator's hand pressing the lever against the guide member to hold the movable jaw in a fixed position.
U.S. Pat. No. 341,503 discloses an adjustable wrench including a fixed jaw, a guide member, a movable jaw, a binding sleeve and a spring. The binding sleeve is biased towards the guide member by the spring and the frictional force therebetween is used to prevent the binding sleeve from sliding along the guide member. The binding sleeve provides a stop surface for the movable jaw to prevent it from moving away from the fixed jaw. One difficulty of this wrench is that this sliding prevention mechanism is not effective when a force of high magnitude is exerted on the movable jaws because it relies solely on the frictional force created by the spring force. Another difficulty is that the wrench has to be adjusted on the object to set the required opening.
Some wrenches utilize not only a spring providing a biasing force against the movement of the movable jaw, but also, teeth on various parts of the wrench providing a better engagement between the movable jaw and the fixed portions of such wrench. U.S. Pat. No. 648,719 discloses an adjustable wrench having a fixed jaw, a guide piece with teeth, and a movable jaw with an arm sliding over the guide piece. The arm includes a triangular catch piece that is biased by a spring to engage the teeth of the guide piece to retain the movable jaw in a fixed position. U.S. Pat. No. 670,890 discloses a fixed jaw, a guide piece, a movable jaw slidable on the guide piece, a lever pivotally attached to the movable jaw having teeth and a spring biasing the lever against the guide piece so that the teeth may engage the guide piece to prevent the movable jaw from sliding on the guide piece when it is set in a fixed position. U.S. Pat. No. 1,185,911 discloses a fixed jaw, a guiding piece having teeth, a movable jaw having teeth adapted to engage the teeth of the guiding piece and the spring biasing movable jaw against the guide piece causing the teeth of the movable jaw to engage the teeth of the guide piece in order to retain the movable jaw in a fixed position. U.S. Pat. No. 1,468,913 discloses a wrench having a fixed jaw, a guide piece having a recess, a movable jaw having an arm adapted to slide in the recess of the guide piece and a spring having a spring finger with teeth adapted to engage corresponding teeth on the arm to keep the arm and the movable jaw in a fixed position. The spring biases the spring finger against the arm of the movable jaw thereby retaining the teeth engagement thereof. The arm of the movable jaw includes also an opening adapted to slide over a crossbar in the recess of the guide piece. The crossbar is shaped accordingly to prevent the pivotal movement of the arm and the movable jaw with respect to the fixed jaw. Furthermore, the surface of the arm opening includes teeth engaging the crossbar when the movable jaw is biased by the spring to the fixed position thereby providing an additional mechanism preventing the movable jaw and its arm from sliding in the recess away from the fixed jaw.
One disadvantage of the aforementioned wrenches that utilize teeth and a spring to provide the biasing force preventing the movement of the movable jaw is that resetting of the movable jaw requires the use of manual force equal to the restoring force of the spring. Therefore, the restoring force of the spring should be limited to one that can be overcome by manual force. Such force is not adequate for the prevention of the displacement of the movable jaw when a very high force is exerted on the nut during a turning operation. However, if such spring were used, it would be extremely difficult to manually adjust the movable jaw.
U.S. Pat. No. 2,774,271 discloses an adjustable wrench having a fixed jaw, a slide piece, a movable jaw sliding along the slide piece and an operating arm pivotally connected to the fixed jaw. In order to maintain the movable jaw in a fixed position, the operating arm is manually biased toward the slide member until its pointed back edge engages teeth present on the movable jaw. Therefore, the movable jaw, due to the engagement of the pointed edge and the teeth, is prevented from sliding along the guide piece. One disadvantage of this wrench is that the biasing force is provided manually and therefore, it may be easily overcome when the turning force reaches a high magnitude resulting in the movement of the movable jaw away from the fixed jaw.
U.S. Pat. No. 3,563,118 includes a fixed jaw, a guide piece, an opening or slide away extending therethrough in a direction perpendicular to the jaw face, a movable jaw having a mounting section adapted to fit in the above mentioned opening and a lever member being operated by hand to regulate the opening formed between the fixed jaw and the movable jaw. Once in a fixed position, the movable jaw is prevented from moving away from the fixed jaw because of the mating engagement between a dovetail portion of its mounting member and a similarly shaped inner portion of the opening of the guide piece. One disadvantage of this wrench is that it lacks stability when a high turning force is experienced because the mating engagement may collapse when such high force is exerted on the movable jaw.
The present invention eliminates the difficulties and drawbacks of the prior art by providing an adjustable wrench with a movable jaw that, during the turning operation, may not be displaced from its designated position when the magnitude of the turning force applied by the wrench on a nut, a bolt head or the like becomes very large. Therefore, this wrench eliminates the troublesome play between the various parts of an adjustable wrench and the accompanying disengagement of the object being turned so that its operation may be performed effectively and efficiently. Furthermore, the present invention provides an adjustable wrench that may be adjusted in precise increments with speed, ease and accuracy without placing the wrench on the object that needs to be turned.
Other objects and advantages of the invention will appear from the following description.